Q-bop vessel construction

ABSTRACT

A Q-BOP steelmaking vessel construction in which tuyeres extending through the bottom wall of the vessel for delivering oxygen to the bath have a diameter not more than 1/13 of the depth of the bath in the converter and the total cross-sectional area of all oxygen tuyeres in the converter in square centimeters is from one to three times the heat size expressed in metric tons.

United States Patent [191 Brisse et al. I

[451 Apr. 9, 1974 g Q-BOP VESSEL CONSTRUCTION [75] Inventors: Andre H.Brisse, Pittsburgh; David K. Griffiths, Penn Hills Twp,, both of Pa.

[73] Assignee: United States Steel Corporation,

Pittsburgh, Pa

[22] Filed: Aug. 29, 1972 [21] App]. No: 284,693

[52] US. Cl. 266/41, 75/60 [51] Int. Cl. C2lc 5/48 [58] Field of Search266/35, 36 P, 41; 75/59, 75/60 [56] References Cited UNITED STATESPATENTS 3,706,549 12/1972 Knuppel et al. 75/60 Primary Examiner-GeraldA. Dost Attorney, Agent, or Firm--Ralph H. Dougherty 57 ABSTRACT A Q-BOPsteelmaking vessel construction in which tuyeres extending through thebottom wall of the vessel for delivering oxygen to the bath. have adiameter not more than 1/13 of the depth of the bath in the converterand the total cross-sectional area of all oxygen tuyeres in theconverter in square centimeters is from one tothree times the heat sizeexpressed in metric tons.

4 Claims, 1 Drawing Figure 1 Q-BOP VESSEL CONSTRUCTION In the bottomblown oxygen steelmaking process, which is known as the Q-BOP process, avessel has a removable bottom or plug which contains one or more tuyeresthrough which oxygen and other gases or particulate matter such as limeor other flux is blown into the vessel. Each tuyere comprises an oxygeninlet tube surrounded by a larger concentric inlet tube for thesimultaneous injection of a jacket gas; which does not re act, or reactsonly slowly with the molten metal in the bath and the material fromwhich the nozzle is 'con structed. This jacket gas acts as a coolantreducing the rate of reaction between the molten metal and the oxygenadjacent to tuyere, preventing rapid erosion of the tuyere, reducing therate of erosion of the lining in the vessel bottom. Thus, the furnacelining and the tuyere wear at the same rate.

South African Pat. No. 691,280 teaches that thetotal cross-sectionalarea of oxygen delivering tuyere pipes in square centimeters should beapproximately equal to the weight of pig iron charged into theconverter'in metric tons. The same reference teaches that the greatestallowable tuyere diameter for vertically mounted tuyeres should notexceed 1/35 of the depth of the bath, assuming an oxygen pressure ofabout 5 to atmospheres'. u

We have discovered that not only can larger tuyeres be used in a bottomblow process, but by increasing the diameter of the tuyeres to l/ ofthebath depth, the number of tuyeres required in a given vessel is onlyone-third thenumber required if the diameter is 1/35 of the bath depth.This results not onlyin a reduced requirement in number of tuyeres, butalso in a reduced number of piping connections for both oxygen andjacketing gas since fewer tuyeres are required. This, in turn, resultsin a decreased manpower requirement for maintenance and periodicreplacement of parts.

It is the principal object of our invention to provide improvedapparatus for refining molten metal in a 0-80? steelmaking vessel.

It is another object of our invention to provide apparatus havingincreased tuyere size over what was heretofore possible.

These and other objects will be more readily apparent with reference tothe following detailed specification and the appended drawing in which:

The single figure is a vertical, cross-sectional view of a Q-BOPsteelmaking vessel.

A bottom blow oxygen steelmaking vessel l0'has a removable bottom 12,comprising a bottom plate 14, and one or more generally upstandingtuyeres 16, which are surrounded by refractory material1'8. The bottomplate 14 is fastened to the furnace by bolts 20. The sides of therefractory portion of the removable bottom do not contact the refractorylining 22 of the vessel, but sufficient clearance is provided around thebottom for inserting a refractory gunning mixture 24to provide a metalancl slag tight seal.

Tuyere 16 is a'dual concentric tuyere composed of an inner tube 30 andan outer tube 34. Tube 30 is spaced from tube 34 by spacers 36, whichmay be weldbeads, spiral wound wire, or any other suitable means formaintaining concentricity. The inner or central tube 30 delivers oxygenand lime to the molten metal bath. The annular space 38 between thecentral tube 30 and the outer tube 34 delivers a jacketing gas which is,in this case, natural gas.

- dard circular, cross-sectional tuyere to about l/l5 of the bath depthapparently reduces the height of the jet of gas in the bath and thusreduces the tendency of spittingto occur in the bath. We have also foundthat the total cross-sectional area of alloxygen delivering tuyeres insquare centimeters may be from one to three times the bath size inmetric tons. 1

The tuyere need not be a standard circular tuyere, but may have any of anumber of cross-sectional shapes such as square, rhombic, rectangular,ellipse, ova], pointed ellipse, or any other desired shape; Todefine acommon parameter of such shapes, we must turn to the terminology offluid mechanics, wherein the hydraulic radius of a non-circularduct isthe fluid-filled area divided .by the insideperimeter of the duct. The

hydraulic diameter equals four times the hydraulic radius. As above, atuyere of any cross section having a hydraulic diameter up to aboutl/l3the bath depth is operable in our invention.

The following examples illustrate the operability of our invention. t 1

XAMPLE.

Circular oxygen tuyere pipes 2.86 centimeters indiameter have beenemployed in a Q-BOP vessel in which the bath depth was approximately 128inches (71.1 centimeters). The hydraulicdiameter was 1/25 the bathdepth. Six tuyeres,.havin'g a total cross-sectional area of the oxygenpipe of 38.5 square centimeters, we're used to blow oxygen into a bathof 18.2 metric tons. Thus, the cross sectional area of the oxygendelivering tuyeres was 2.11 times the bath size inmetric tons.

' EXAMPLE 11 Circular oxygen tuyere pipes having an internal diameter of2.323 inches (5.9 centimeters) were employed'in a Q-BOP vessel in whichthe bath depth was 32 inches (81.3 centimeters). The hydraulic diameterwas I/ 14 the bath depth. Twotuye'res having a total cross-sectionalarea of the oxygen pipe of 52.8 square centimeters were used to blowoxygen into abath of 23 metric tons. The cross-sectional area of theoxygendelivering tuyeres was 2.3 times the bath size in metric tons.Oxygen flow was 11,400 scfm (2352 Nm /hr.) at 15 psig.

Our invention comprehends the broad range of hydraulic diametersfromabout 1' inchto 2.85 inches or 2.5 centimeters to 7.5centimeters.However, we prefer ahydraulicv diameter in the'range of about 1.6 to2.5inches or 4.0 to 6.5 centimeters. We prefer a large hydraulic radiussince it willaccommodate low pressures. Low oxygen pressures requirelarge tuyeres to obtain sufficient oxygen throughput to operate therefining process. Of course the pressure must be sufficient to overcomethe ferrostatic head of molten metal in the vessel. We have found thatthe oxygen pressure must be maintained at a. minimum of 1 atmosphere andcan be as high as 15 atmospheres. The oxygen throughput mustbe at leastnormal cubic meters per hour per square centimeter of oxygen tuyerecross section.

The tuyere pipes may be installed atan angle with respect to the axis ofthe 0-801 converter vessel to improve mixing or impart rotation to thebath thus, minimizing sloshing and "bath instability. In this case, tu'-yeres of even larger cross-sectionalarea may be used. For instance, thetuyere diameter may be increased about percent for nozzles inclined tothe vessels vertical axis. The tuyere pipes may also be installed in thesidewall of the converter beneath the surface of the molten metal bath.

From the foregoing it is readily apparent that we have invented animproved Q-BOP vessel for refining molten metal in which tuyeresextending through the bottom wall of the vessel have a hydraulicdiameter no greater than 1/13 of the bath depth and a totalcross-sectional area of the oxygen delivering portion of such tuyeres insquare centimeters from 1 to 3 times the bath size in metric tons.

We claim:

1. A vessel for refining a molten metal bath contained therein, saidvessel having an opening in its upper portion and at least one tuyereextending vertically through the bottom wall of said vessel forintroducing refining gas to said bath, each tuyere having a hydraulicdiameter from l/25th to 1/ 13th of the bath depth and having a totalcross-sectional area of all such refining gas tuyeres in cm from one tothree times the bath size in metric tons.

2 A vessel according to claim 1 in which each refining gas tuyere has ahydraulic diameter from about 2.5 centimeters to 7.5 centimeters.

3. A vessel according to claim 1 in which each refining gas tuyere has ahydraulic diameter from about 4.0 to 6.5 centimeters.

4. A vessel according to claim 1 wherein each refining gas tuyere issurrounded by a larger concentric outer tube which forms with saidtuyere an annular passage for simultaneous injection of a jacket gasinto the molten metal bath.

1. A vessel for refining a molten metal bath contained therein, saidvessel having an opening in its upper portion and at least one tuyereextending vertically through the bottom wall of said vessel forintroducing refining gas to said bath, each tuyere having a hydraulicdiameter from 1/25th to 1/13th of the bath depth and having a totalcross-sectional area of all such refining gas tuyeres in cm2 from one tothree times the bath size in metric tons.
 2. A vessel according to claim1 in which each refining gas tuyere has a hydraulic diameter from about2.5 centimeters to 7.5 centimeters.
 3. A vessel according to claim 1 inwhich each refining gas tuyere has a hydraulic diameter from about 4.0to 6.5 centimeters.
 4. A vessel according to claim 1 wherein eachrefining gas tuyere is surrounded by a larger concentric outer tubewhich forms with said tuyere an annular passage for simultaneousinjection of a jacket gas into the molten metal bath.